Decouple root visitors from object visitors.

src/heap/scavenger.h

Index: src/heap/scavenger.h
diff --git a/src/heap/scavenger.h b/src/heap/scavenger.h
index 54fe6ffdf92f50b4a017bd4216b0005011b542a6..72e6a1f4743fa286769708e39fdf851adc13cfa5 100644
--- a/src/heap/scavenger.h
+++ b/src/heap/scavenger.h
@@ -44,16 +44,20 @@ class Scavenger {
   VisitorDispatchTable<ScavengingCallback> scavenging_visitors_table_;
 };
 
-
 // Helper class for turning the scavenger into an object visitor that is also
 // filtering out non-HeapObjects and objects which do not reside in new space.
-class ScavengeVisitor : public ObjectVisitor {
+// TODO(ulan): ObjectVisitor is needed only for code flusher. Remove it after
+// changing the scanvenger to treat JSFunction->next_link strongly.
+class RootScavengeVisitor : public ObjectVisitor, public RootVisitor {
  public:
-  explicit ScavengeVisitor(Heap* heap) : heap_(heap) {}
+  explicit RootScavengeVisitor(Heap* heap) : heap_(heap) {}
 
   void VisitPointer(Object** p) override;
   void VisitPointers(Object** start, Object** end) override;
 
+  void VisitRootPointer(Root root, Object** p) override;
+  void VisitRootPointers(Root root, Object** start, Object** end) override;
+
  private:
   inline void ScavengePointer(Object** p);